I think i forgot to mention i am talking about my action camera, i dont think the K5 can do the same my Osmo action camera can do, like 4K / 60 FPS and 100 mbit, just to mention the 2 biggest things in regard to details.
Also you cant easy change in between recording options easy as you can with a action camera, so you should stick to one set of formats.
I assume the K5 have the same segment size as most dashcams, so if i was a biker i would stick to the 3 min segments i have always used in my car.
Of course that do mean you will have to drop a lot of files into a editing software to output them as one big file, but once you get used to it, it are not that hard to work with.
I have compiled a few drive sessions recorded in my car with a action camera, the longest was a 9 hour long drive, which i split up into 9 segments, and then mixed to 6 X speed so the 1 hour of driving only was 10 minutes to watch.
You are not going to get anyone to sit glued to a screen and watch for hours on end, normally peoples attention start to fade around the 10 - 15 minute mark, so my advise is to use accelerated speed, and maybe mix in some highlights in normal speed or awesome photos taken.
30 or 60 FPS you can speed up just fine, so you can get some ground covered, it will be fine for long stretches where nothing much change, other times you want normal speed, but these are all things you can play with in post production.
In regard to memory card size i would go for a 256 GB card for a system like the K5, that should still hold a pretty decent drive before it start to loop back on itself when the card are full.